1. Field of the Invention
The present invention relates to a data recording apparatus for recording data on recording media, such as a digital video camera or a digital still camera for recording image-captured data, to a method for controlling the data recording apparatus, and to a computer program and, in particular, relates to a data recording apparatus for performing an operation of recording data on recording media in a plurality of use modes in such a manner that a user performs image capturing while holding the data recording apparatus in his/her hand or with the main unit thereof being fixed to a tripod, to a method for controlling the data recording apparatus, and to a computer program.
More particularly, the present invention relates to a data recording apparatus for recording data on recording media in such a manner that a read/write head carries out a seeking operation on a recording surface as in the case of, for example, a hard disk, thereby enabling random access, to a method for controlling the data recording apparatus, and to a computer program and, in particular, relates to a data recording apparatus in which the risk of damage to the apparatus is reduced by retracting the head from the recording surface of a disk when the apparatus is dropped on the basis of the detection result of an acceleration sensor or the like, to a method for controlling the data recording apparatus, and to a computer program.
2. Description of the Related Art
With the development of information technology, such as information processing and information communication, there has arisen a necessity to reuse information that was created and edited in the past. For this reason, information storage technology has become increasingly important.
Until now, information recording apparatuses using various media, such as magnetic tapes and magnetic disks, have been developed and become popular. In disk-type recording media, such as hard disks, basically, random access is possible by performing an operation in which a read/write head carries out a seeking operation in a radial direction on the recording surface of a rotating disk.
Hard disks have already become widely popular. For example, as standard local recording apparatuses for personal computers, in order to install various types of software, such as an operating system (OS) and application programs, which are necessary to start up a computer, and in order to store various kinds of data files that are created or edited, hard disks are used.
Furthermore, also, for information devices that handle data of a large size such as digital video cameras, hard disks have come to be used as local recording apparatuses or externally provided recording apparatuses (see, for example, Japanese Unexamined Patent Application Publication Nos. 2007-208864 and 2007-87469). When a hard disk is used for a recording device of a digital video camera, digital recording of many items of high-quality image data and random access to recorded data are possible. Furthermore, connection can be made to a computer, so that files can be manipulated or images can be edited in the computer. Furthermore, recently, hard disk drives are used for operation devices that are designed under the assumption that they are to be carried by a user on the move as in portable music playback devices and devices installed in mobile bodies such as navigation devices. By using a hard disk for these information devices, it is possible to decrease the weight, the volume, and the cost of the device when compared to the case in which a removable magnetic tape or optical disc is used. In addition, since the device is not limited by the size of the recording medium and the layout of the removable unit, miniaturization of the device is realized and the degree of freedom of design is increased.
For hard disk drives, a technology is used in which an air layer is created between a magnetic disk and a magnetic head as a result of the rotation of the magnetic disk on which a magnetic substance has been applied or deposited, causing the magnetic head to slightly float. That is, when the magnetic disk is stopped, the magnetic head is lightly in contact with the magnetic disk surface. The flow of air that occurs with the rotation of the magnetic disk causes the magnetic head to float, and recording and reproduction are performed. While non-contact between the magnetic disk and the magnetic head is maintained, magnetic recording at a high density is realized by decreasing the distance between the disk and the head.
With such a mechanism, hard disk drives are considered to be recording apparatuses that are vulnerable to impact. In particular, in a case where a hard disk drive is installed in a device that is operated while being held as in a digital camera or a portable device, when a user drops the device by mistake during operation, the risk of damage is high in that the head and the disk are brought into contact with each other due to impact when the device collides with the floor surface.
For this reason, some portable devices installed with a hard disk drive incorporate a scheme in which falling is detected by using an acceleration sensor, and the head is retracted before the device collides with the ground surface, thereby protecting the hard disk drive.
Furthermore, in information devices installed with a hard disk drive, an intermittent recording method is often applied from the viewpoint of lower power consumption. For example, when image capturing is to be performed using a digital camera, the hard disk drive is placed in an idle state, image-captured data is temporarily stored in the buffer memory, and the hard disk drive is set to an active state only during the period in which data stored in the buffer memory is output and recorded in the hard disk. Here, the hard disk drive is vulnerable to changes in the external environment in the active state. However, in the idle state, the rotation of the disk is stopped, and the head is fixed at the retraction position. Therefore, the probability of withstanding an impact is high. Accordingly, an information processing apparatus and an image-capturing apparatus have been proposed in which when it is determined on the basis of the detection result by the acceleration sensor or the like that the apparatus is in a state in which it is difficult to perform safe data recording, the apparatus does not enter an active state, and the idle state of the hard disk drive is maintained (see, for example, Japanese Unexamined Patent Application Publication No. 2007-208864).
As a processing method for accurately determining whether an apparatus is falling, a method for predicting a state in which the apparatus begins to freely fall by using both an acceleration (gravity state) at the current time, which is detected from an acceleration sensor, and a history of acceleration changes has been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2007-87469). By retracting the head at a predicted timing at which the apparatus begins to freely fall, it is possible to avoid damage to the hard disk.
According to the above-described prediction method, it is possible to suitably predict a state in which the user loses hold of a portable device and the portable device begins to fall. However, modes in which image capturing is performed using a digital camera include a case in which the main body thereof is fixed to a tripod or the like and image capturing is performed in addition to a case in which a user holds a digital camera by hand and image capturing is performed. Between when the digital camera begins to freely fall and when the tripod on which the digital camera is mounted falls over, the acceleration (gravity state) detected by the digital camera and the history of the acceleration changes differ. For this reason, a fall detection algorithm for detecting whether the digital camera is falling has a problem in that it is incapable of performing accurate prediction when a tripod is fixed.